Stress-Compensating Pick-Up Tool for PIC Chip Curvature Alignment
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Solution Overview
Problem
Existing stress compensation methods for photonic integrated circuits (PICs) are limited by passive tools that cannot finely correct curvature issues in singulated dies, leading to alignment challenges during assembly, especially when adhesive curing introduces additional curvature, and are not compatible with all dicing methods.
Innovation Solution
A stress compensating pick-up tool with a tool tip and actuator that rotates opposite tip portions to actively align and straighten companion chips with respect to host chips using vacuum tubes and a piezoelectric actuator, allowing for real-time optical alignment feedback and force adjustment to ensure precise alignment before adhesive curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If passive stress compensation layers are applied to the backside of the wafer, then the wafer can be straightened to a planar surface, but the singulated die cannot be finely corrected or adapted for during later assembly
Solution Approach 1:
The pick-up tool incorporates an actuator that can dynamically adjust the curvature of the companion chip during assembly. This transforms the static, fixed curvature determined during wafer fabrication into a dynamically adjustable parameter, allowing fine correction and adaptation during the assembly process to achieve precise optical alignment.
Solution Approach 2:
The system uses optical alignment feedback to monitor the alignment between companion chip and host chip waveguides. Based on this feedback, the actuator adjusts the companion chip curvature in real-time, creating a closed-loop control system that ensures precise alignment while accommodating variations in wafer bow and adhesive curing effects.
2Manufacturing precision
If the wafer thickness is adjusted using backside grinding, then the stress compensation layer can be modified, but it removes the stress compensation layer or adds complexity to the wafer process flow
Solution Approach 1:
The patent replaces the mechanical backside grinding process with a stress compensation layer deposited on the frontside of the wafer. This substitution eliminates the need for complex backside processing while achieving the same stress compensation effect, thereby simplifying the overall process flow.
Solution Approach 2:
Instead of applying stress compensation to the backside of the wafer as in conventional methods, this invention applies the stress compensation layer to the frontside of the wafer. This inversion of the conventional approach simplifies the process by eliminating backside grinding while maintaining effective stress compensation.
3Ease of manufacture
If some dicing methods are used, then specific wafer backside surface finish is required, but they are not compatible with the stress compensation layer
Solution Approach 1:
The patent inverts the conventional approach by applying the stress compensation layer to the frontside of the wafer rather than the backside. This allows the backside to maintain the surface finish required for various dicing methods while the frontside stress compensation layer provides the necessary stress management, thereby resolving the incompatibility issue.
4Productivity
If the singulated die is left as-is after singulation, then the process is simple, but adhesive curing or host chip cavity alignment may require fine tuning of the curvature of the die
Solution Approach 1:
The pick-up tool with actuator enables dynamic curvature adjustment of the companion chip during assembly. This allows the system to maintain simple, fast assembly processes while achieving precise optical alignment by adjusting the companion chip curvature in real-time based on alignment requirements, resolving the trade-off between speed and precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The tool enables precise optical alignment and compensation for curvature issues, ensuring accurate waveguide alignment between companion and host chips, even with bowed or convex wafer shapes, simplifying the assembly process and improving the reliability of PIC integration.
Implementation Method 1
two vacuum tubes extending through the tool tip, wherein a vacuum connection is created via the vacuum tubes to hold the companion chip by the tool tip
Implementation Method 2
The actuator is a piezoelectric actuator
Data Source
AI summary
A stress compensating pick-up tool for aligning a companion chip with a host chip includes a tool tip and an actuator. The tool tip holds the companion chip, and includes a first tip portion and a second tip portion. The actuator applies a force to the tool tip, wherein the force causes the first tip portion and the second tip portion to rotate in opposite directions with respect to one another to optically align a portion of the companion chip with a corresponding portion of the host chip.